The present invention relates to organic compounds for providing improved bioavailability of drugs and nutrients by permiabilising cell membranes of organisms, in particular animals and fish. The improved organic compounds may be used as an animal or fish feed additive to increase, for example, nutrient and pigment uptake.
Previously lysophospholipids and phospholipids have been added to animal feeds to act as growth enhancers by increasing the uptake of nutrients, to increase pigment absorption and for the nanoencapsulation of drugs for drug delivery in vivo. For example, International Patent Application No. PCT/GB93/00736 in the name of David Garnett describes an animal feed containing a substantially pure lipophilic, phospholipid component which is introduced into the stomach cell membrane of an animal to increase the porosity of the membrane.
Lysophospholipids and phospholipids are available as purified natural compounds and as a result are substantially impure. Thus, artificial organo-phosphorous compounds have been synthesised for use as an animal feed by reaction of a long chain alkyl acid chloride with an organophosphonic acid derivative, as described in GB231191A and PCT/GB97/01020.
However, the use of such organophosphorous compounds as animal feed additives has a number of drawbacks. Firstly, the synthesis of pure organophosphorous compounds is expensive and difficult to prepare on a large scale. Additionally, the use of compounds containing a valence five phosphorous as a feed additive is environmentally unfriendly and may have toxicological effects on the organism to which it has been administered.
It is an object of the present invention to provide improved organic compounds for use as feed additives which overcome the abovementioned drawbacks for increasing the uptake of selected compounds, such as nutrients and pigments.
Accordingly, the present invention provides a fish feed additive comprising an acylamino acid for combining with a substance to enhance the bio-availability of thate substance in the fish by permabilisation of cell membranes of the fish, the acylamino acid having the general formula: 
wherein
R1 is hydrogen, a primary, secondary or tertiary alkyl or alkenyl group and
R2 is hydrogen, a straight or branched chain alkyl group or a straight or branched chain substituted alkyl group, the substituents being selected from thio, thioether, hydroxy, carboxy, quarternary ammonium, amide, heterocyclic, benzyl, substituted benzyl, amino, substituted amino groups and difunctional alkyl groups linking to the nitrogen atom of the peptide bond.
Preferably, R1 is a long chain alkyl group having at least 10 carbon atoms. For example, being a lauroyl (CH3(CH2)10), palmitoyl (CH3(CH2)14) or a stearoyl group (CH3(CH2)16). Alternatively, R1 may be a long chain alkenyl group, such as an oleate (CH3(CH2)7CHxe2x95x90CH(CH2)7). R2 may be the side chain of any amino acid but preferably is a short chain alkyl group having 1 to 4 carbon atoms, such as a methyl or ethyl group.
A preferred acyl amino acid for incorporating into the feed additive of the present invention is 2-palmitoylaminoproprionic acid.
The compound may be in the form of a powder for incorporation into the feed, for example being mixed with a suitable carrier such as silica talc, be in the form of capsules or be dissolved in water for drinking.
The substance that combines with the acylaminoacid to enhance its bioavailability is preferably a pigment.
The compound is preferably provided in synthetic form.
The present invention will now be further illustrated by means of the following Example and accompanying drawings.
It has been found that acyl amino acids increase the uptake of selected compounds into organisms by permabilising the cell membrane. The acyl amino acids preferably contain a long chain alkyl or alkenyl group, such as a palmitoyl or oleate group led to an amino acid, such as glycine, alanine, valine, threonine or methionine.